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Stock-Based Employee Compensation (Details 3)	12 Months Ended
Stock-Based Employee Compensation (Details 3)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock-Based Employee Compensation
Dividend yield	1.50%	0.00%	0.00%
Expected stock price volatility	46.00%	46.00%	45.00%
Risk-free interest rate	1.10%	2.60%	2.60%
Expected option life	6 years	6 years	6 years

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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